Parallel control immunohistochemical analyses confirmed the presence of ATM and Chk2 proteins, and also nuclear positivity for the key DNA damage mediator protein 53BP1 in at least 70% cells of all medulloblastomas as well as in control normal brain tissues (Table 2 and data not shown), suggesting that defects of these tumour suppressor proteins, at least at the level of protein expression and nuclear localization, are likely rare. Here, CHEK2 is linked to medulloblastoma.